A forked version of Manik's script that avoids issues stashing when only untracked files are present (i.e. old branch that has not had git ignores updated)

gitsyncupstream.sh

#!/bin/bash

####################################################################################
#
# This script syncs your private, personal checkout with an upstream repository.
#
###################################################################################

# This is where your local, priave copy is checked out
LOCAL_REPO=${HOME}/Code/infinispan/my_repo

# The git path to the upstream repo.  This is a read-only repo.
UPSTREAM_REPO="git://github.com/infinispan/infinispan.git"

# The refspec to the remote copy of your private repo.  This is origin by default.
REMOTE_REPO=origin

#### ---- functions
need_stash() {
  status=`git status --porcelain --untracked-files=no`
  if [ "z$status" == "z" ] ; then
    eval "${1}='FALSE'"
  else
    eval "${1}='TRUE'"
  fi
}

sync() {
  branch=${1}
  git checkout -f ${branch}
  stash=''
  need_stash stash

  if [ $stash == "TRUE" ] ; then
    git stash
  fi
  git pull -q ${UPSTREAM_REPO} ${branch}
  git push -q ${REMOTE_REPO} ${branch}
  if [ $stash == "TRUE" ] ; then
    git stash pop
  fi
}

get_branches() {
  flags=""
  if [ ${2} == "remote" ] ; then
    branches=`git branch -r | grep ${REMOTE_REPO} | sed -e "s/*//g" -e "/HEAD/d"`
  else
    branches=`git branch | sed -e "s/*//g"`
  fi

  i=0
  for b in ${branches} ; do
    cl=`echo ${b} | sed -e "s:${REMOTE_REPO}/::g"`
    eval "${1}[${i}]=${cl}"
    let "i=${i} + 1"
  done
}

localize() {
  rb=$1
  if [ $rb == "HEAD" ] ; then
    echo "Not processing HEAD"
  else
    local=$2
    echo "Localizing $rb"
    found="FALSE"
    for l in ${local[*]} ; do
      if [ $found == "FALSE" ] ; then
        if [ $l == $rb ] ; then
          found="TRUE"
        fi
      fi
    done

    if [ $found == "FALSE" ] ; then
      echo "... adding a local branch for $rb"
      git checkout -q -f -b $rb ${REMOTE_REPO}/$rb
    else
      echo "... no need to add local branch for $rb"
    fi
  fi
}

### --- end functions


cd ${LOCAL_REPO}

init_stash=''
need_stash init_stash

if [ $init_stash == "TRUE" ] ; then
  git stash
fi
git fetch -q ${UPSTREAM_REPO}
git fetch -q ${UPSTREAM_REPO} --tags

get_branches local_branches local
get_branches remote_branches remote

for rb in ${remote_branches[*]} ; do
  localize $rb "${local_branches[*]}"
done

unset local_branches
get_branches local_branches local

## Sync branches
for local_branch in ${local_branches[*]} ; do
  sync $local_branch
done

## Sync tags
git push -q ${REMOTE_REPO} --tags
 
if [ $init_stash == "TRUE" ] ; then
  git stash pop
fi